1. Field of the Invention
The present invention relates, to an ink ribbon cassette which is designed to be detachably loaded in a recording apparatus having a recording head, such as a printer and a facsimile. The invention also relates to a recording apparatus which can be loaded with such an ink ribbon cassette.
2. Related Background Art
Known recording apparatus of the type mentioned above usually has an ink ribbon cassette detachably loaded on a carriage which also carries a recording head and moves to the left and right along a platen. In general, the ink ribbon cassette has an ink ribbon supplied by a supply reel and taken up by a take-up reel. In operation, the ink ribbon is fed along an ink ribbon path, which is in front of the recording head, so as to be taken up by the take-up reel.
When the ink ribbon cassette is loaded on the carriage, the take-up reel is drivingly connected to a ribbon driving shaft provided on the carriage, so that the ink ribbon is fed in synchronization with the movement (scan) of the carriage during the recording.
This type of ink ribbon cassette is required to eliminate any dead space in the cassette so as to minimize the volume in the cassette for a given length of the ink ribbon. It is also required that the ink ribbon cassette is mounted as closely as possible to the platen, in order to minimize the stroke of the recording head's up and down motion thereby to reduce the size of the whole recording apparatus.
In recent years, the multi-color recording apparatus finding spreading use are those having a plurality of ink ribbon cassettes stacked in stages. The design of this type of recording apparatus has encountered difficulty in using ink cassettes of the same design and size for all stages of the ink ribbon. In addition, the size of the whole apparatus is inevitably increased due to the use of such a stack of ink ribbon cassettes.
Ink ribbon cassettes are also required to smoothly feed the ink ribbon Without any looseness or slack. In other words, it is essential that a suitable level of tension is applied to the ink ribbon during the feeding thereof.
The conventional ink ribbon cassette, however, tends to allow the ink ribbon to become slack, particularly at the portion in the vicinity of the reading head when an acceleration, deceleration or other impact results from dynamic motion of the movable parts, such as up and down motion of the recording head, reversing of the carriage, and vertical shifting of the stack of ink ribbon cassettes in the multi-color recording apparatus. Such a slack of the ink ribbon may cause a jam of the apparatus with the ink ribbon, resulting in a recording failure.
The ink ribbon cassette should be designed and constructed to allow the ink ribbon to be precisely fed without any looseness or slack. This essentially requires that the ink ribbon is taken up by a constant tension.
In the known ink ribbon cassettes, the means for maintaining tension on the ink ribbon is comprised of a friction pad which is resiliently pressed onto the ink ribbon. This type of tensioning means provides an equal level of frictional resistance against forward movement, i.e., the movement in the take-up or feeding direction and backward movement of the ink ribbon. Therefore, it has been often experienced that the ink ribbon is moved backward when an impact is applied due to, for example, up and down motion of the recording head, with the result that the ink ribbon undesirably comes off the predetermined path of feed of the ink ribbon.
The friction pad is usually supported by a leaf spring having a considerably large length such that the tensioning means requires a considerably large space for the installation thereof.
The multi-color recording apparatus making use of an ink sheet (including ink ribbon) is generally sorted into the following types: a first type in which a plurality of ink ribbon cassettes each having a ribbon of the required color are stacked one on another; a second type in which a wide ribbon having a width which is equal to the product of the recording line width and the different colors are arranged is in such a manner that the ribbon is striped, that is, with a plurality of regions parallel to the longitudinal or feeding direction of the ribbon such that the respective regions have different colors; and a third type in which a narrow ink ribbon having a width corresponding to the recording line width is sectioned in the longitudinal direction thereof such that sections of different colors are successively formed on the ribbon.
When a multi-color ink sheet is used, it is necessary to provide a suitable detecting means capable of detecting what color is set in the recording position.
A conventional detecting means includes a color sensor disposed upstream of the recording position. This type of detecting means, however, has a drawback in that, when a a portion of the ink ribbon of a specific color is sensed, the sensed portion has not reached yet the recording position. Thus, the recording system employing this type of sensor essentially requires that the ink sheet (ribbon) is fed wastefully to bring the sensed portion of the ink ribbon to the recording position.
More practically, when this type of sensing means is used, a control is conducted such as to feed the ink ribbon precisely by an amount which corresponds to the distance between the position where the color sensor is located and the recording position or, alternatively, when a delicate control of the ink ribbon feed is impossible, the ink ribbon is roughly fed by an amount which is considered sufficient for bringing the sensed portion of the ink ribbon to the recording position.
Thus, the recording apparatus employing the known multi-color ink ribbon encounters difficulty in precisely and promptly bringing the desired color to the recording position. In addition, it is very difficult to detect any erroneous feeding, e.g., such an error that a portion of an image to recorded in a color A is wrongly recorded in another color B.